Switching regulators or direct-current to direct-current (DC-DC) voltage converters (i.e., DC-DC converters) commonly include a pulse frequency modulation (PFM) component in a feedback loop having pre-determined reference voltages and comparators. For example, in one approach, the feedback loop includes two comparators receiving two reference voltages as inputs, which adds design complexities, but does not provide the highest power efficiency (e.g., η). Power efficiency η is defined as the ratio of the output power (e.g., Po) over the input power (e.g., Pi) wherein the input power Pi is equal to the output power Po plus the dissipated power (e.g., Pd). Mathematically, η=Po/(Po+Pd). Further, the comparators and the reference voltages in this approach are customized for each specific application.
In another approach, a pulse representing a time when the output driver is on is issued with a pre-determined width when the output voltage Vo is below a reference voltage (e.g., a threshold voltage) Vref. As a result, the pulse width is fixed
In another approach, two reference voltages are used to determine the idle time period when the output driver is off. This time period is then used to adjust the reference voltage. The response time to transients on supply and load current, however, is slow, and the dynamic adjustment is not available.
In another approach, the output voltage of the switching regulator is not efficiently utilized, e.g., it is lower or higher than the demand voltage from the device (e.g., processor) utilizing the regulator.
Like reference symbols in the various drawings indicate like elements.